1. Field of the Invention
The present invention relates to an image analysis method and image analysis apparatus.
2. Description of the Related Art
Conventionally, an image analysis method called FCS (Fluorescent Correlation Spectroscopy) is known. The FCS is described in, for example, “New Concept in Correlator Design”, Klaus Sch tzel, Inst. Phys. Conf. Ser. No. 77, P175, 1985. In the FCS, one or a plurality of measurement points in a sample are intermittently irradiated with excitation light for a certain period of time (for example, 10 sec), and intensity fluctuations of fluorescence emitted from the measurement points are detected to execute correlation analysis, thereby estimating molecular numbers and diffusion constants.
Also, an image analysis method called RICS (Raster Image Correlation Stereoscopy) is known. The RICS is described in, for example, “Measuring Fast Dynamics in Solutions and Cells with a Laser Scanning Microscope”, Michelle A. Digman, Claire M. Brown, Parijat Sengupta, Paul W. Wiseman, Alan R. Horwitz, and Enrico Gratton, Biophysical Journal, Vol. 89, P1317 1327, August 2005. In the RICS, a fluorescent image is acquired by detecting fluorescence generated while raster-scanning excitation light with respect to a sample. Data of each pixel in the fluorescent image represents information of an intensity of fluorescence generated from a corresponding point in the sample. That is, pixel data respectively have different acquisition times and acquisition positions. By executing spatial correlation analysis using pixel data, diffusion constants and molecular numbers are calculated.
It is preferable to form an image by mapping pieces of information obtained from a large number of measurement points of a sample so as to examine these pieces of information in association with positions in the sample.
When measurements are done using the FCS by setting a large number of measurement points on a sample, and measurement results are mapped, a time difference between the first and last measurement points is large, and mapping results include large errors due to the influence of temporal changes, and lack reliability. For example, when molecular numbers or diffusion constants are to be mapped for 256×256 measurement points, assuming that a time required to obtain a molecular number or diffusion constant per measurement point is 10 sec, a long measurement time of 256×256×10 sec is required. Even when measurement results having such long temporal differences are mapped, the mapping results become insignificant in practice.
In the RICS, although pieces of information are obtained from a large number of points in a sample, one information (for example, a molecular number or diffusion constant) per image is merely calculated in general. That is, the RICS naturally does not acquire a plurality of pieces of information from a scanning region. For this reason, the RICS does not consider mapping of acquired information.